Miniaturized or small-scale fluid processing units, especially for multiple unit operations as chemical processing devices have been developed for military, automotive, and remote applications where size and weight limitations are important considerations. Typical applications include heating and/or cooling devices, fuel processors, and chemical synthesis units.
As shown in U.S. Pat. No. 5,611,214 entitled MICROCOMPONENT SHEET ARCHITECTURE, miniaturization is accomplished with micromachining microchannels onto a laminate. Laminates are stacked to form systems. This approach has also been shown in U.S. Pat. Nos. 4,392,632, 4,386,505, for refrigerators. U.S. Pat. No. 5,690,763 and WO 97/14497 (PCT/US96/16546) show microchannels on laminae for chemical processes. A disadvantage of this "laminate" approach is the cost of the micromachining and the limited dimensions of the microchannels depending upon the type of micromachining process selected. More specifically, the dimension that is limited is the thinness of the fin between channels that may be achieved with machining. The machining forces necessarily require that the fin have sufficient thickness to withstand the machining process which may be thicker than a thermal optimal design.
An alternative form of "stacked" plates may be found in U.S. Pat. Nos. 5,455,401 and 5,620,616 for a plasma torch electrode. A stacked arrangement is also found in U.S. Pat. No. 5,016,707 for a multi-pass crossflow impingement heat exchanger.
Thus, the present state of the art offers the choices of multiple unit operations in a laminate structure that is expensive or single unit operation in a stacked structure that is less expensive. Accordingly, there is a need in the art for a method of making a fluid processing unit capable of multiple unit operations that is less expensive.